1. … DME DME reacts to form alkenes
DME adsorbs to acid sites forming ‘methyalting species’
DME

2. … DME DME reacts to form alkenes
CH3OH
Alkenes attack methylating species to form alkoxides, rejecting methanol (or water)
DME adsorbs to acid sites forming ‘methyalting species’
DME

3. Methylation: Deprotonation of alkoxide forming alkene

4. Methylation: Deprotonation of alkoxide forming alkene; alkene attacks methylating species

5. Hydride Transfer: Alkene donates H to alkoxide leading to alkane
Methylation: Deprotonation of alkoxide forming alkene; alkene attacks methylating species

6. Hydride Transfer: Alkene donates H to alkoxide leading to alkane and (eventually) arenes
Methylation: Deprotonation of alkoxide forming alkene; alkene attacks methylating species

7. Hydride Transfer: Alkene donates H to alkoxide leading to alkane and (eventually) arenes
Methylation: Deprotonation of alkoxide forming alkene; alkene attacks methylating species
Skeletal Isomerization: Very slow due to formation of unstable carbocationic transition states

8. Hydride Transfer: Alkene donates H to alkoxide leading to alkane and (eventually) arenes
“+CH3” X
b-scission occurs at C8+ X
Methylation: Deprotonation of alkoxide forming alkene; alkene attacks methylating species
Skeletal Isomerization: Very slow due to formation of unstable carbocationic transition states

9. … + + + + “H+” “H+” “H+” “H+” + “H+” “CH3” “CH3” “CH3” “CH3” “CH3”

10. . . . bn = HTn HTn + Men … 473 K, 1 bar, H-BEA (Si:Al = 12.5:1)
13C-dimethyl ether:12C-alkene = 140
HTn . + +
“H+”
“H+” …
“CH3”
“CH3”
HTn
bn = .
HTn +
Men
Men
Mole fraction
Mole fraction
Number 13C atoms
Number 13C atoms

11. High termination probability at triptane and isobutane
1.0
473 K, 1 bar, H-BEA (Si:Al = 12.5:1)
13C-dimethyl ether:12C-alkene = 140 + + + +
HTn
bn =
“CH3” +
“CH3” +
HTn +
Men
0.5
Second characteristic of reaction pathway: Low TP for small species and high TP at triptane indicates fast propagation up to triptane with fast termination at triptane. Explains high selecticvity to tritpane. + + + +
0.0 2 3 4 4 5 6 7 n

12. + Homologation of Ethanol/Diethyl Ether C4: n-butanes C10
C6: methyl-pentanes
C8: dimethyl-hexanes
methyl, ethyl-pentane
C10: trimethyl-heptanes
dimethyl, ethyl-hexanes
diethyl, methyl-pentanes

13. +
Ethanol and Diethyl ether dehydrate to ethylene without subsequent homologation (or oligomerization)
C10

14. +
Ethanol and Diethyl ether dehydrate to ethylene without subsequent homologation (or oligomerization)
Mixture of ethanol or diethyl ether (to generate ethylene) and dimethyl ether (generate methylating species) produces only dehydration products
C10

15. +
Ethanol and Diethyl ether dehydrate to ethylene without subsequent homologation (or oligomerization)
Mixture of ethanol or diethyl ether (to generate ethylene) and dimethyl ether (generate methylating species) produces only dehydration products
Does dimethyl ether methylate ethylene?
C10

16. High termination probability at triptane and isobutane
1.0
473 K, 1 bar, H-BEA (Si:Al = 12.5:1)
13C-dimethyl ether:12C-alkene = 140 + + + +
HTn
bn =
“CH3” +
“CH3” +
HTn +
Men
0.5 + + + +
0.0 2 3 4 4 5 6 7 n

17. High termination probability at triptane and isobutane
1.0
473 K, 1 bar, H-BEA (Si:Al = 12.5:1)
13C-dimethyl ether:12C-alkene = 140 + + + +
HTn
bn =
“CH3” +
“CH3” +
HTn +
Men
0.5 + + ~0 + + +
0.0 2 3 4 4 5 6 7 n

18. High termination probability at triptane and isobutane
1.0
473 K, 1 bar, H-BEA (Si:Al = 12.5:1)
13C-dimethyl ether:12C-alkene = 140 + + + +
HTn
bn =
“CH3” +
“CH3” +
HTn +
Men
0.5 +
Me3
= 15 +
Me2 ~0 + + +
0.0 2 3 4 4 5 6 7 n

19. vs.
vs.
vs.
Increasing alkene size and changing shape
vs.
vs.
Protonated oxygenate versus methyl species
Alkene attacking alkoxide versus surface methylating species

21. How does HT/M change with changing alkene size/shape?
Is there a difference in reactivity of surface methyl species and protonated DME molecules?
What is the difference between reaction of alkene with alkoxides and protonated ether molecules? (Is there something ‘special’ about C1 surface groups?)
I think that you want to emphasize also how the rates methylation vs. hydrogen transfer change with alkene size (CHECK). What is actually the methylating surfaces species, why ethene does not ethylate as fast as ethanol (and the latter does not survive). This is aquestion of whether alkoxides vs. H-bonded alkanols/ethers are the better alkylating agents and why.